Bearings in which an inner race or spindle is supported within a surrounding outer race or hub by two axially spaced rows of rolling elements provide superior axial stiffness and load support. As a consequence, they are almost universally used for automotive wheel bearings, driven or non driven. The two rows of rolling elements are most often bearing balls, in modern designs, with convergent, angular contact pathways.
The manufacturer of two row ball bearings that support heavy loads must deal with the issue of retaining at least one separable ball race to the spindle. This is because, while it is simple to load a full complement of balls into the first row, the second row will have to have one pathway that is axially removable. Otherwise, the second row would have to be loaded with a technique such as radially displacing the spindle and hub and then loading the balls into the locally widened space so created. This allows for only a less than full complement of balls in the last installed ball row, which would drastically reduce load capacity. With a separable race, a full ball complement is achieved, but two other issues must be dealt with. The separable race must be installed so as to maintain a proper bearing preload or endplay and must be securely retained axially to the end of the spindle. In some older methods of assembly, both considerations are handled by the same structure. For example, a simple threaded nut can be torqued down against the separable race, pushing it axially against its ball row until the proper bearing preload is achieved. If the nut can be prevented from backing off by an adequate locking means, it both maintains the preload and retains the race. Nut locking is difficult to assure, however.
A more accurate and secure, if more complex system is disclosed in co assigned U.S. Pat. No. 4,179,167 issued Dec. 18, 1979 to Lura et al. A separable race slides onto the outer surface of the spindle freely until it hits the outer ball row. As it makes contact with the outer ball row, its outer edge rests past the inner wall of a groove machined into the spindle. The separable race is forced and held against its ball row by an assembly apparatus to the desired preload, and then the axial spacing of its outer edge from the outer wall of the groove is accurately gauged. Then, a pair of selected thickness keeper rings, chosen from a pre machined assortment, are tightly inserted between the outer edge of the separable race and the far wall of the spindle groove. The keeper rings hold the proper race location and so maintain the preload or end play as desired. Finally, a sleeve shaped retaining ring must be swaged down over the keeper rings to hold them radially down into the groove. While this assembly method has proved a solid and robust design for years, a less costly system, in terms of parts, assembly steps, or both, would be very desirable, if it could provide the same preload accuracy and durability.
The simplest possible separable race retention system, at least in terms of the total number of parts, is one that uses some portion of the spindle material itself to retain the separable race instead of a separate component, such as a nut or keeper rings. One such process that has received a good deal of attention in patents world wide is the so called cold forming or "riveting" process, illustrated in FIG. 1 of the drawings in the subject application. As seen in FIG. 1, what is proposed is to make the outboard ball row 10 run on a pathway that is integrated to a separable race 12 that also includes the wheel attaching flange. The outer annular face of the separable race 12 is ground flat, smooth and perpendicular to the central axis of spindle 18. A deformed bead or "collar" 16 is cold formed axially over the flat outer face of the separable race 12 to retain it axially to the spindle 18. How solidly and securely the separable race 12 is retained to the spindle 18 is a function not only of the degree of radial overlap between the bead 16 and the face of the race over which it is formed, but also a function of the continuity of contact between the inner, cylindrical mounting surface of the separable race 12 and the outer cylindrical support surface of the spindle 18. Their mutual contact interface should be both tight and continuous, that is, with no radial gap.
Even when continuous, gap free mutual contact between the mating cylindrical surfaces of the separable race and the spindle is achieved, however, the problem remains of preventing the separable race from turning or twisting on the spindle under bearing load. A smooth surface to surface contact resists turning only by virtue of the tightness and pressure of contact at the interface, which may work loose with time. One design, disclosed in U.S. Pat. No. 4,986,607 issued Jan. 22, 1991 to Hofmann et al, deals with the race turning problem by machining teeth or splines into the annular outer face of the separable race. The deformed bead of the spindle, as it is cold formed into a retention bead, it is concurrently formed into interlocking engagement with the teeth. This interlocking configuration resists race turning better than a simple friction fit between a smooth, flat race face and overlapping bead would do. The main drawback of such a system is the cost and difficulty of machining in separate splines or teeth into the separable race, which would have to be separately cut. Also, the bead would have to be cold worked very thoroughly and with a good deal of pressure to assure that it filled in around the sharp teeth.